The Gordon Research Conference on Bioenergetics is held biannually and is coordinated with the European Bioenergetics Conference (EBEC) which meets in alternate years. This Gordon Conference is the major meeting in the United States that is devoted to a large spectrum of research in the area of bioenergetics. Although it is focused on molecular mechanisms in oxidative phosphorylation and membrane transport, this Gordon Conference also covers closely related areas of investigation that are physiologically oriented. For instance, in recent years, sessions have been devoted to mitochondrial myopothies; and the involvement of mitochondria in apoptosis. In the 1999 conference, the use of genetic engineering to bypass a genetic defect in the NADH dehydrogenase in a mammalian cell culture line will be highlighted in the session on complex I. Since 1994, the crystal structures of F1-ATPases, cytochrome c oxidases and cytochrome bc1 complexes have been elucidated. This detailed structural information has provided the basis of rationally designed experiments to probe structure-function relationships using directed mutagenesis as the primary tool. This approach has provided new insights on the coupling of electron transport in cytochrome oxidase, conformational changes in the cytochrome bc1 complex during electron transport and rotational catalysis in the FoF1-ATP synthase which will be presented. A session on generation and consumption of proton gradients by single proteins and a session on the mechanisms of various ATPases performing different kinds of work will complement the sessions dealing with the electron transport complexes and the FoF1-ATP synthases and V-ATPases, respectively. Since this Gordon Conference is the major international meeting on bioenergetics that is held in the United States, young American bioenergenicists are actively recruited as participants to provide them with an opportunity to interact with top investigators in the field.